Traveling prop system for a mine working face having a steep,or semi-steep,or flat orientation



Oct. 27, 1970 K. GRE

TRAVELING PROP SYSTEM FOR A MINE WORKING FACE vHAVING A STEEP.SEMI-STEEP. OR FLAT ORIENTATION Filed March 1o, 1969 FIG. 1.v

Bhf h3! V32 g |-33 34-1 l 35m2 l I A v if FIG. 6. 53, y 7 1 5-.53-5-2!Si #14 t l :l L 43 46 5755'65 646352'436l4543 4l l l l l l I INVENTOR 36z BY KONRAD GREBE I I i eww, Mfg,

ATTORNEYS.

United States Patent O U.S. Cl. 299-32 17 Clailns ABSTRACT OF THEDISCLOSURE A traveling prop system useful in connection with miningmachinery comprising a multiplicity of prop containing frames driven bysuitable piston cylinder means and including ladder means comprisingstringers disposed in front of and behind the frames joined together byrung means suitably attached to the floor and/or roof beams. The miningmachinery may be attached to the forward Stringer as a guide rail.

. A traveling prop system has been proposed for working faces,preferably those having a steep or a semi-steep orientation, whichconsists of a series of frames which are attached to a ladder-likemember extending through the breast in such a manner as to preservetheir spacing along the downgrade. During their advancement, the framesare held by the ladder-like member through connecting rods, and thestringers of the ladder extend between the rows of the props of thetraveling prop system.

The use of connecting rods has the disadvantage that, during theiradvancement, the frames have to perform a swinging movement. This bringsit about that the beams of the successive frames have to be spaced apartalong the downgrade so as to permit this swinging movement. Precisely inthe case of steep and semi-steep orientation, however, it is importantto cover the full area of the roof as well as the floor with the beams,so as to prevent the development of pits in the floor or roof due tobreak-outs, thereby providing a poor basis for the proper setting of theadvanced frames under pressure between the floor and the roof. But evenin a level orientation, when the roof or oor are poor it may bedesirable to have complete iloor and roof coverage. Under allcircumstances it is desirable to advance the frames along the roof andfloor, straight in the direction of advancement, while maintaining anelastic contact pressure. A swinging movemeut, however, practicallyrequires the operator to loosen the frames from the roof and oorcompletely during their advancing movement.

Another disadvantage of the prior proposal consists in the fact thatfirst all frames have to be advanced in some desired sequence bycorresponding swinging movements, before the ladder-like member can bemoved forward, and a simultaneous swinging movement of all connectingrods in the opposite direction is then necessary for this purpose. Tomake it at all possible to fetch the ladder-like member forward in theymanner contemplated, all frames must previously have performed a step ofthe same size. In other words, a certain invariable step length must beobserved; but this is difficult to accomplish when the forward stepentails a swinging movement. The swinging movement of the ladder and thearrangement of its stringers inside of the rows of props excludes thepossibility of using the stringers of the ladder for the guidance of amining apparatus or for the hanging of a gob curtain.

It is the aim of the invention to overcome these disadvantages anddifliculties.

The invention relates to a traveling prop system for a working face,preferably for a working face having a steep or semi-steep orientation,comprising a succession of frames which are connected, in a mannerassuring their downgrade spacing from one another, to a ladderlikemember extending through the breast. The invention is characterized inthat the rung-like elements associated with the ladder-like members liedisplaceably on the floor beams of the frames and are guided by thelatter in their longitudinal displacement. The ladder-like memberspreferably have a restricted vertical movement with the stringers of theladder being disposed in front of the front row of props of thetraveling prop system and in back of the rear row of props. At the sametime, the floor beam of each frame can be located between two successiverungs of the ladder-like member, or else it may have a recess in whichonly one rung associated with it is guided. Of course, the beams areguided by rungs, or the rungs are guided by the beams, in a reciprocalmanner, depending on which of the two is being moved.

It is desirable that a second ladder-like member of the same kind beassociated with the roof beams of the frames in order to guide them.This second ladder-like member can be replaced, when the traveling propsystem is used in semi-steep and steep orientations, by other guidingmeans between the roof beams of the successive frames; when thetraveling prop system is used in level orientations, such replacementmay be required, under certain circumstances.

By constructing the traveling prop system according to the invention, itis possible to guide, one or the other all of the frames of a travelingprop system extending over the entire length of the breast, by means ofthe ladder-like members, in a manner which has hitherto been possibleonly in the case of the reciprocal guidance of two frames combined in asingle chock. The frames can move straight forward, always in thedirection of their beams, and the beams can follow one another withoutany appreciable amount of space in between them, and consequently avirtually complete coverage of the roof and oor can be achieved in thedirection of both dip and strike, to a far greater extent than'hashitherto been possible. It is possible to advance the frames While theyare applying an elastic tension between the roof and the floor, and nolonger is a separate period required for the advancement of theladder-like member.

Instead, it is desirable for an advancing cylinder extending lengthwiseof the beam to be associated with each beam of each frame. The pistonsare fastened to elements of the ladder (rungs or stringers) and thecylinder is fastened to the beam, or vice versa. If the successiveframes are now alternately set and released, and if they are alternatelyset forward and backward in relation to one another, it is desirable toperform the advancement of the traveling prop system so that, while theforward frames are set under pressure between the roof and the door, theladder rungs associated with the roof beams of said forward frames aredisplaced along the beams of these frames towards the working face, theladders with the relieved rear frames associated with the rest of theirrungs are pulled along by the same amount and the rear frames are againadvanced along their rungs by the same amount. The set frames located atthe leading end of the rungs at the beginning of the advancing periodare now at their trailing end, and the released frames originallylocated at the trailing end of the rungs are now at the leading end ofthe advanced rungs. Now, when these frames are set and the other framesare released, it is possible to continue the advancement of thetraveling prop system in a virtually continuous manner.

The breast-side Stringer of the ladder can be constructed as a guidingrail for a winning apparatus, and

the gob-side stringer can be constructed as a rail for hanging a goblcurtain or mat. It is desirable for these rails to have individualsections which can flex against one another at least upwardly, becauseit cannot be expected that the floor and the roof of the seam will havean entirely uniform inclination over their entire length, or for thatmatter, even an uniform inclination through the entire advancing cycle.If the changes in the course of the seam that occur in the area of theroof differ from the simultaneous changes in the area of the floor, thecorrect position of the frames in relation to the bedding might beadversley influenced by the fact that the distance of the roof beamsfrom one another and the distance of the floor beams from one anotherare kept constantly invariable by the stringers, even though theposition which the succeeding beams assume in relation to one another asregards height is different in the area of the roof from what it is inthe area of the lloor. In order nevertheless to permit an always correctposition of the frames in relation to the bedding, the stringers of theladder associated with the roof beams have telescoping rail sectionswhose length is variable by the operation of adjusting devices.

The manner in which the rungs are joined to the stringers of the laddermust always provide a certain amount of play, as must also the manner inwhich the guiding surfaces of the beams are joined to the stringers. Theladder will hang from the set frames, and each of the released frameswill hang from the ladder. That is, in the case of the set frames, playwill occur between the beams and the rungs and between the rungs and thestringers in the downhill direction of the breast (below the beams), andin the case of the released and advancing frames, there will be play inthe upward direction of the breast (above the beams). If the advancedframes are then set in this position, the ladder, after the release ofthe other frames, will shift with these frames downhill in the breast,i.e., upon each setting and releasing action, the prop system will driftdownhill by a certain amount.

No matter how slight this amount might be, it can, on account of theconstant repetition of the process, prove to be intolerable, even if anattempt is made to compensate the drift by angling the frames to someextent in respect to the direction of advancement. It is, thereforeproposed to provide elastic elements between cooperating contactsurfaces associated with the stringers on the one hand and with thebeams on the other. These elastic elements -urge the beams and rungsuphill to such an extent that play exists between beams and rungs andbetween rungs and stringers only in the downhill direction. That is, theelastic elements must be strong enough to hold the individual frame thathas been released in the plane of the ladder at the height at which itwas previously located in relation to the ladder.

The same applies accordingly in the vertical plane of the frames asregards the play which the rungs of the ladder have in relation to thebeams. It is desirable for this play to be compensated for by elasticelements which tend to displace the rungs associated with the roof beamsin the direction of the roof (the ladder associated with the floor beamsis urged towards the floor by its own fweight). The elevation of theladders thus varies only when such variation is required byirregularities in the course of the roof and/ or floor. While it isalways only one of the two groups of frames that is set, while the otheris tensed elastically between the roof and the floor, the stringers ofthe ladders are always urged only to a certain extent elasticallytowards the roof or floor, as the case may be, by the springs in thecase of the roof and by the weight of the ladders in the case of thefloor, and the total strength of these springs must be suflicient tobear the weight of the ladder associated with the roof beams. 'Ihepressure of the ladders against the roof can be augmented by making thesprings stronger, and the bearing contact of the other ladder againstthe floor can be augmented by additional springs at the iloor beams.

If the greatest possible coverage of the roof and floor area is to beachieved, care must be taken to see that the widths of the beamscorrespond approximately to the spacing of the rungs, if only one rungis associated with each beam, or to the spacing of the pairs of rungs iftwo rungs are associated with each beam, etc. Care must also be taken tosee that the advancing cylinders associated with the beams have only avery short stroke. In the case of complete coverage of the roof and oor,and in the case of the maintenance of an elastic contact pressure duringthe advancing of the frames, there is no objection to breaking down longsteps of the frames into a number of short steps performed alternatelyby frames A and B. On the contrary, in this manner it is possible alwaysto sustain an especially favorable prop resistance per square meter ofcovered surface. The steps of the frames can furthermore be made soshort that it is not only possible to advance all frames Asimultaneously and then to advance all frames B simultaneously, but alsoit is possible first to advance the series of frames A successively andthen advance, one after the other, the frames B situated alternatelybetween them.

The new traveling prop system is especially suited for use inconjunction with a mining method in which a kerfing and ripping chain iscarried on controllable and lixable rails laid along the floor and roof.To understand the advantages `which the construction according to theinvention offers for this method of mining, it is necessary at thispoint rst to present an explanation of the process itself and of thediiculties which have hitherto caused problems in its application.

With the kerfng and ripping chain there are associated elements whichcut kerfs and elements that rip, the kerling elements producing kerfsthat are made progressively deeper into theseam along the roof andlloor, and after the kerf has reached the proper depth, a ripping toolmounted on the same chain rips away the working face between the kerfs,advancing it by a corresponding amount.

For example, seven kering groups, each cutting the kerf S mm. deeper,are followed in each case by a ripper which advances the working face by56 mm. A working face is thus produced which is of a sawtooth shape, theripper forming in each case the tip of such a sawtooth. It takes awaythe undercut part of the working face, and it is followed by another setof kerf cutters which again undercut the new Working face, which, onaccount of the sawtooth shape of the face, runs somewhat at an angle tothe kerng and ripping chain guide rails, until the next ripper againadvances the working face, and so on. The kerng elements are fastened toScrapers which keep the kerf and the space between the chain and theworking face free of the lines produced by the kerfng. Since the spacebetween the guiding rail and kerng and ripping chain, on the one hand,and the working face on the other, becomes progressively narrower due tothe sawtooth shape of the working face, the Scrapers arranged insuccession along the chain must become progressively thinner in thatportion of them that extends between the chain and the working face. Asthe mining progresses, the prop system on which the mining apparatus issupported by the rail or channel guiding the kerfing and ripping chainis continuously advanced. Assuming that the successive ripping tools,each of which advances the working face by 56 millimeters, are spaced 56meters apart from one another, then in the same time in which the chainmoves forward l meter in its guide, the traveling prop system would haveto be advanced one millimeter, in order that the working face mightalways have the same sawtooth shape and that the ripping tools mightalways rip to the same depth. Hitherto it has been possible to achievethis only by letting the front side of the Scrapers lie ilat against theworking face and constantly urging the set of frames A, on which theguide rail of the kerling and ripping chain was fastened, against theworking face by means of feed cylinders supported by the set frames B.When these feed cylinders reached the end of their excursion, the mininghad to be interrupted for the purpose of bringing up (advancing) framesB. Another disadvantage resides in the fact that the constant contactpressure of the scraping tools against the coal face produced a constantfriction, and the friction losses involved, which only served forcontrolling purposes, substantially impaired the efficiency of thekerling and ripping chain drive.

Now, if the same mining apparatus is associated with the traveling propsystem according to the invention, a double advantage is achieved. Inthe first place, the interruptions for the purpose of advancing frames Bare eliminated, since the stringers of the ladder-like members, whichare constructed as guide rails for the kerng and ripping chain, are nowjoined both to frames A and to frames B, and they are advancedcontinuously and with complete uniformity both during the advancement offrames A (B) and during the bringing up and pushing forward of frames B(A). In the second place, however, there is no longer any need to laythe Scrapers at against the working face in order to provide for thecorrect depth of penetration of the keriing and ripping tools, becausethe proper control can also be assured by a precise metering of the feedof the frame being advanced in each case.

Assuming that the kerng and ripping chain is moved forward at a speed of1 m./s., provision must be made according to the above example for ametering of the feed so that the stringers of the ladder are pushedforward at a rate of 1 mm. per second.

Assuming that advancing cylinders are associated with the beams offrames A and the beams of frames B, whose pistons have a stroke of 50mm., that the props of the set frames A are disposed 5() mm. ahead ofthe props of the released frames B and that the advancing cylinders bothof frames A and of frames B are fed by metering cylinders, the pressurechamber of each advancing cylinder is times the size of the pressurechambers of the associated metering cylinders, then, according to ourexample, the metering cylinders would have to be cycled every 5seconds;'they would then produce a piston movement of 5 mm. in theadvancing cylinder for each cycle, and, after ten cycles of meteringcylinder operation, i.e., after 50 seconds, the pistons of all of theadvancing cylinders would be in their end position, the ladder wouldhave advanced 50 mm., and frames B would have passed from a position 50mm. behind frames A, over a distance of 100 mm. into a position 50 mm.ahead of frames A. Then, by reversing the hydraulic pressure in thelines feeding the props of frames A and B, frames B would have to be setand frames A would have to be released, and the advancement of thetraveling prop system would thus continue uniformly and at the sametempo. The progression of mining in this manner is more uniform than inthe case of a flat support of the Scrapers against the working face,since the working face can still be ripped out, and the friction lossesproduced by the Scrapers on the breast are avoided.

Needless to say, the Scrapers must still be constructed so that theirupper edge is in contact with the working face. Otherwise they could notkeep the space between the chain and the working face clear of nes.Above or below this edge, however, there is no longer any need for asurface extending all the way to the floor and to the root` and restingagainst the working face. Instead, the edges can project beyond theactual body of the Scrapers and can be provided with a clearance angle,so that the scraper can cut freely at all times.

If it is assumed that the excursion of the advancing cylinderscorresponds to the active width of the ripping device associated withthe mining system, the above considerations relating to the rate of feedof the advancing cylinders can be expressed by saying that, if theripping apparatus associated with a kerng and ripping chain are equallyspaced apart, the rate of excursion of the advancing cylinder isregulated by metering cylinders, which are to be cycled preferably inuniform sequence, in such a manner that a full stroke of the advancingcylinder, which corresponds to n full strokes of the metering cylinder,takes place in the same period of time in which the kertng and rippingchain covers a distance corresponding to the distance between tworipping members on the kerng and ripping chain.

The prop system according lto the invention is thus, on the one hand,especially suitable for the performance of the mining process justdescribed, while on the other hand, this method of mining, whichconstantly clears a small but uniform alleyway ahead of the travelingprop system, offers a particularly good opportunity for the use of theprop system according to the invention.

If a breast, in which the prop system and the mining proceed in thismanner, has to be slowed, an adjustable apparatus can be associated witheach advancing cylinder, by which the excursion of its piston can belimited. The advancing cylinders associated with the wing that has toturn are in each case fully extended; at the other end of the breast theadvancing cylinder is blocked, and at the frames between them the systemthat limits the stroke is so adjusted that, starting from the pivotpoint, the stroke is slightly larger in each succeeding advancingcylinder. As soon as this stroke has been completed, the advancingcylinder and the metering cylinder feeding it are automatically blocked,so that the keriing tools and ripping tools associated with the kerngand ripping chain no longer attack the working face at these points.

The annexed drawings show embodiments of the traveling prop systemaccording to the invention. Understanding of this invention will befacilitated by reference to the drawing, wherein:

FIG. 1 is a plan view, partially in section along line I-I of FIG, 3 ofa portion of an apparatus in accord with this invention;

FIG. 2 is a side elevation of the same apparatus;

FIG. 3 is a front elevation (as seen from the breast), partially insection along linev III- III of FIG. 1 of the apparatus of thisinvention;

FIG. 4 shows, on a reduced scale, a schematic view of the advancement ofthe prop system of this invention and the shape of the working face whenthe stringers associated with the traveling prop system according to theinvntion are used for the guidance of a kerfing and ripping c am;

FIGS. 5 and 6 are supplementary to FIG. 4, showing how the kerf in theworking face is produced when the kerng tools arranged between therippers are set close together, and when they are uniformly spread out,respectively.

According to FIGS, 1, 2 and 3, prop frames A and prop frames B aredisposed alternately in the downhill direction along the breast. In theperiod of operation shown in the drawing, frames A are set and frames Bare relieved. In the lower half of the igure, the prop system isrepresented in its position at the beginning of the advancing cycle, andin the upper half of the gure it is represented at the end of theadvancing cycle. Frames A as Well as frames B have roof beams 1 and 'oorbeams 1. Beneath the roof beams 1 and above the oor beams 1 there aredisposed on either side thereof, a web 2 (2'), and rungs 11 (11') of aladder Whose breast-side stringers are formed by guide bars 12 (12') ofa mining apparatus which is not shown, and whose gob-side stringers 13(13') serve for the hanging of a gob curtain 21. The props of frames Aare marked 3 and those of frames B are marked 4. Props 3 and 4 aremounted in prop sockets 5 and 5' which are associated with the beams 11') and are provided with lateral gussets 6 and 6' having apertures inwhich the rungs 11 and 11' are carried in a vertically displaceablemanner. The rungs 11, 11', which are associated with the same beam, arein turn fastened together by crossbars 14, 14. These crossbars 14 14',are engaged by the piston rods 15, of advancing cylinders whose jackets7, 7, marked 8, 8', in the case of frames B) are in turn fastened to thewebs 2, 2', of the beams.

In the advancing period represented in FIG. 1, the props 3 of the framesA are set and pressure is delivered to the gob-side chambers of cylinder7, 7', associated therewith. Props 4 of frames B, however, are eitherrelieved of pressure or are held by light elastic pressure between theroof and the floor, and hydraulic pressure is delivered to thebreast-side chambers of their associated cylinders 8, 8'. At thebeginning and at the end of the advancing cycle, therefore, the frames Aare in the same place, but the ladder Stringing together frames A and Bhas, by the end of the cycle, advanced one step laterally along therungs of this ladder. In the next cycle, therefore, the frames B, whichare now ahead of the frames A, are set, and pressure is delivered to thegob-side chambers of their associated cylinders 8, and to thebreast-side chambers of cylinders 7 associated with the now releaseframes A. At the same time, each full stroke of the pressure cylinder 7(8) can correspond to n strokes of a preceding metering cylinder, whichis not shown, so that the tempo of the advancement of all frames A and Band the tempo of the advancement of the ladder can be made completelyuniform.

If the roof beams of the ladder are provided with a verticalarticulation, the associated rungs can also have an articulation.Besides, between the rungs of the ladder and the breast-side stringers12, 12', of the ladder, it is desirable to provide a verticalarticulation 16, 16', so as to make it possible to bring the guide bars12, 12', provided for the mining apparatus, into the desired positionfor the advancement of the working face, using for that purpose acontrolling means 17, which in the drawing appears only in the area ofthe roof beams. Similar articulations can be provided for joining therungs to the gob-side ladder stringers 13, 13'. Also represented in thedrawing is a coal shield 22 cooperating with a chute 23.

The breast-side stringers 12, 12', of the ladder are preferably in theform of a channel in which a winning apparatus can be guided. Thischannel is divided into sections 18, 18', which are joined together byvertical articulations 20. At the roof, these channel sections haveportions 19 telescoping inside of them so that they can be lengthenedand shortened to some extent. It is desirable not to leave the length ofeach such rail section 18-19 to arbitrary movement of the section inrelation to one another, but to adjust such in a predetermined manner.Accordingly, the gob-side stringers 13, 13', are formed of extensiblesections at the roof and of sections of constant length on the floor,which are joined together by vertical articulations. The cross-sectionof the breastside stringers, however, does not have to be that of achannel.

The individual channel or guide-bar sections have bearing surfacesagainst which springs 24, 25, rest, which in turn act upon bearingsurfaces on the roof and floor beams 1, 1', so that they seek todisplace the beams, and consequently the prop frames A or B with whichthey are associated, in an uphill direction along the breast. Thesesprings are represented only diagrammatically, as are also theadditional springs 26 which act 0n the rungs 11 of the ladder and urgesuch against the roof.

FIG. 4 shows, on a greatly reduced scale, longitudinally of the breast,in a purely diagrammatic manner, how the powered prop system advanceswhen its breast-side stringers are used to guide a kerng and rippingchain. The solid line 31 shows the position of the guide bar 12 (i.e.,its rear edge) at the beginning of the advancing cycle; the broken line32 shows the position of the guide bar after it has been advanced onehalf step; solid line 33 shows the shape of the coal working faceproduced by the rippers at the beginning of the advancing 8 cycle, andbroken line 34 shows the position of this working face after the propsystem has been advanced by the amount stated.

While the prop system is advancing continuously and uniformly under theeffect of the metering cylinder from line 31 to line 32, the rippersguided in channel 12 move continuously and uniformly in the direction ofthe arrow. At the beginning of the advancing cycle they are at points 35and 36, where the line 33 breaks to form a sawtooth. It is assumed thatthe depth of cut of each ripper (i.e., the height of each sawtooth)corresponds to a full step of the power prop system, as shown in FIG. l;it is furthermore assumed that there is such a coordination between theadvancement of the power prop system and the movement of the rippersthat the rippers, during one full step of the prop system, cover adistance that is the same as the distance between them, i.e., thedistance between points 35 and 36. After a half step of the power propsystem, therefore, the rippers have covered half of this distance andhave moved from point 35 to point 37 and from point 36 to point 38,while maintaining their distance from the channel 12 that is guidingthem, so that the working face now has the shape indicated by the brokenline 34.

FIGS. 5 and 6 offer a visualization of how the kerf preceding theworking face is produced, from which the rippers supported at the roofand iloor by the flanges of rails 12 and 12 respectively win the coaland advance the working face. There is shown a leading edge 41 of aguide rail or channel 12; the rippers 45 and 46 carried on the guiderail; a working face 43 produced by these rippers; and kerfers 51 to 57and 51' to 57' are disposed between the rippers. These kerfers are set,according to FIG. 5, immediately in front of ripper 46, and, accordingto FIG. 6, between the rippers 45 and 46, 58 represents the depth of thekerf made by the kerfers, 59 designates the depth of the kerf after thepower prop has advanced one full step and the kerfers have been moved onin the direction of the arrow by an amount corresponding to the spacebetween the rippers. There are shown Scrapers 61 to 67 and 61' to 67 towhich the kerfers 51 to 57 and 51 to 57', respectively, are fastened.The proiile of these Scrapers is designed in each case so as to coverthe distance from the front edge of the rail 12, represented by line 41,to the working face represented by line 43. The system represented inFIG. 6 is somewhat different from the one shown in FIG. 5.

What is claimed is:

1. A traveling prop system for use with a mine working face comprising asuccession of interconnected spaced prop containing frames, ladder meansinterconnecting such frames, loor beams under said frames, roof beamsover said frames, rung means of said ladder means displaceably disposedon said floor beams and guided by said floor beams with respect tolongitudinal displacement, and Stringer means of said ladder meansdisposed both in front of the front row of props and in back of the backrow of props of said prop system.

2. A traveling prop system as claimed in claim 1 for use with a gradedmine working face including predetermined down grade spacing of saidframes.

3. A traveling prop system as claimed in claim 1, wherein said rungmembers have limited vertical displaceability.

4. A traveling prop system as claimed in claim 1 including second rungmeans operatively associated with said roof beams.

5. A traveling prop system as claimed in claim 1 includingcylinder-piston drive means associated with each frame, wherein saidcylinder is attached to said floor or room beams and said piston isattached to said ladder means.

6. A travelling prop system as claimed in claim 1 includingcylinder-piston drive means associated with each frame, wherein saidcylinder is attached to said ladder means and said piston is attached tosaid floor or roof beams.

7. A traveling prop system as claimed in claim 1, wherein said Stringermeans of said ladder means disposed in front of the front row of propsis a guide rail for mining apparatus.

8. A traveling prop system as claimed in claim 1, wherein said Stringermeans of said ladder disposed behind the back row ofthe props is a gobcurtain hanging rail.

9. A traveling prop system as claimed in claim 1, wherein said Stringermeans are upwardly pivotable.

10. A traveling prop system as claimed in claim 4, wherein said secondrung means have second stringer means associated therewith which areadjustable telescoping members. I

11. A traveling prop system as claimed in claim 4 including elasticmembers disposed between said second rung means and said roof beams.

12'. A traveling prop system as claimed in claim 4, wherein said roofbeam width is substantially the same as the distance between adjacentrung means.

13, A traveling prop system as claimed in claim 1, including a kei-lingand ripping chain mining apparatus guided by said forward Stringermeans.

14. A traveling prop system as claimed in claim 13, wherein the eiectivewidth of said ripping apparatus is substantially equal to the stroke ofcylinders associated with said frames.

15. A traveling prop system as claimed in claim 13, includingsubstantially equally spaced ripper members on said chain.

16. A traveling prop system as claimed in claim 15, including meteringmeans controlling the rate of extension of said cylinders and means forcycling said cylinder in substantially uniform time sequence, whereby afull stroke of said cylinder corresponding to n strokes of a cylinder insaid metering means takes substantially the same time as the time ittakes for said kerng and ripping apparatus to cover the distance betweenadjacent ripper members on said chain.

17. A traveling prop system as claimed in claim 14, including adjustablemeans adapted to limit the length of the excursion of a pistonassociated with said frames.

References Cited UNITED STATES PATENTS 3,362,169 1/ 1968 Groetschel61--45 FOREIGN PATENTS 999,943 7/ 1965 Great Britain.

ERNEST R. PURSER, Primary Examiner U.S. Cl. X.R. 299--33; 61-45

